<template>
  <el-color-picker
    v-model="theme"
    :predefine="['#409EFF', '#1890ff', '#304156','#212121','#11a983', '#13c2c2', '#6959CD', '#f5222d', ]"
    class="theme-picker"
    popper-class="theme-picker-dropdown"
  />
</template>

<script lang="ts">
    const version = '2.3.7' // element-ui version from node_modules
    const ORIGINAL_THEME = '#409EFF' // default color
    export default {
        data() {
            return {
                chalk: '', // content of theme-chalk css
                theme: ''
            }
        },
        computed: {
            defaultTheme() {
                return this.$store.state.settings.theme
            }
        },
        watch: {
            defaultTheme: {
                handler: function(val, oldVal) {
                    this.theme = val
                },
                immediate: true
            },
            async theme(val) {
                const oldVal = this.chalk ? this.theme : ORIGINAL_THEME
                if (typeof val !== 'string') return
                const themeCluster = this.getThemeCluster(val.replace('#', ''))
                const originalCluster = this.getThemeCluster(oldVal.replace('#', ''))
                console.log(themeCluster, originalCluster)
                const $message = this.$message({
                    message: '  Compiling the theme',
                    customClass: 'theme-message',
                    type: 'success',
                    duration: 0,
                    iconClass: 'el-icon-loading'
                })
                const getHandler = (variable, id) => {
                    return () => {
                        const originalCluster = this.getThemeCluster(ORIGINAL_THEME.replace('#', ''))
                        const newStyle = this.updateStyle(this[variable], originalCluster, themeCluster)
                        let styleTag = document.getElementById(id)
                        if (!styleTag) {
                            styleTag = document.createElement('style')
                            styleTag.setAttribute('id', id)
                            document.head.appendChild(styleTag)
                        }
                        styleTag.innerText = newStyle
                    }
                }
                if (!this.chalk) {
                    const url = `https://unpkg.com/element-ui@${version}/lib/theme-chalk/index.css`
                    await this.getCSSString(url, 'chalk')
                }
                const chalkHandler = getHandler('chalk', 'chalk-style')
                chalkHandler()
                const styles = [].slice.call(document.querySelectorAll('style'))
                    .filter(style => {
                        const text = style.innerText
                        return new RegExp(oldVal, 'i').test(text) && !/Chalk Variables/.test(text)
                    })
                styles.forEach(style => {
                    const { innerText } = style
                    if (typeof innerText !== 'string') return
                    style.innerText = this.updateStyle(innerText, originalCluster, themeCluster)
                })
                this.$emit('change', val)
                $message.close()
            }
        },
        methods: {
            updateStyle(style, oldCluster, newCluster) {
                let newStyle = style
                oldCluster.forEach((color, index) => {
                    newStyle = newStyle.replace(new RegExp(color, 'ig'), newCluster[index])
                })
                return newStyle
            },
            getCSSString(url, variable) {
                return new Promise(resolve => {
                    const xhr = new XMLHttpRequest()
                    xhr.onreadystatechange = () => {
                        if (xhr.readyState === 4 && xhr.status === 200) {
                            this[variable] = xhr.responseText.replace(/@font-face{[^}]+}/, '')
                            resolve()
                        }
                    }
                    xhr.open('GET', url)
                    xhr.send()
                })
            },
            getThemeCluster(theme) {
                const tintColor = (color, tint) => {
                    let red = parseInt(color.slice(0, 2), 16)
                    let green = parseInt(color.slice(2, 4), 16)
                    let blue = parseInt(color.slice(4, 6), 16)
                    if (tint === 0) { // when primary color is in its rgb space
                        return [red, green, blue].join(',')
                    } else {
                        red += Math.round(tint * (255 - red))
                        green += Math.round(tint * (255 - green))
                        blue += Math.round(tint * (255 - blue))
                        red = red.toString(16)
                        green = green.toString(16)
                        blue = blue.toString(16)
                        return `#${red}${green}${blue}`
                    }
                }
                const shadeColor = (color, shade) => {
                    let red = parseInt(color.slice(0, 2), 16)
                    let green = parseInt(color.slice(2, 4), 16)
                    let blue = parseInt(color.slice(4, 6), 16)
                    red = Math.round((1 - shade) * red)
                    green = Math.round((1 - shade) * green)
                    blue = Math.round((1 - shade) * blue)
                    red = red.toString(16)
                    green = green.toString(16)
                    blue = blue.toString(16)
                    return `#${red}${green}${blue}`
                }
                const clusters = [theme]
                for (let i = 0; i <= 9; i++) {
                    clusters.push(tintColor(theme, Number((i / 10).toFixed(2))))
                }
                clusters.push(shadeColor(theme, 0.1))
                return clusters
            }
        }
    }
</script>

<style>
  .theme-message,
  .theme-picker-dropdown {
    z-index: 99999 !important;
  }
  .theme-picker .el-color-picker__trigger {
    height: 26px !important;
    width: 26px !important;
    padding: 2px;
  }
  .theme-picker-dropdown .el-color-dropdown__link-btn {
    display: none;
  }
</style>
